How do you answer that?!

[Midland Retty]

Therefore a system designer could still comply fully with the recommendations of BS5839-1 in providing a system where the complete failure of one of the sounder circuits means that there is virtually no alarm sound level in large areas of a building during a fire condition.

Thanks for confirming that Wiz

It was something I was unaware of, and a tad concerning if I'm honest

That said I take on board your points that sounder failures are, for the most part, few and far between so I suppose it has to be taken in context.
 

[Tom W]

I really appreciate everyones participation in this, thank you very much

[Wiz]

BS5839-1 seems to assume that a sounder circuit or its components is unlikely to severely fail for anything other than by damage caused during a fire.
I'm sure many people might argue that this is somewhat short-sighted, but there it is.

[Mike Buckley]

Or does BS5839 pt 1 assume that any failure in the sounder circuits, outside a fire condition, should be picked up in the weekly test?

There is only so far you can go with the belt, braces, safety pin, bit of string etc. The whole thing has to be balance between the likelyhood of the problem occuring and the cost of curing it. It seems to me that one of the major problems with alarm systems is unwanted alarms rather than the failure of the alarm.

[Big_Fella]

If the circuit fails, this will be monitored so would be displayed at the CIE.  If the internal conponents fail on an individual sounder this may not be hightlighted at the CIE until the weekly test is undertaken.  Even then it may not be picked up if persons are not near the sounder to recognise its failure.  It's no different to a conventional detector, where the internal parts may fail or may not sense 'smoke'.  This may not be picked up by the CIE until the device is physically tested during maintenance.

I don't think the odd device failure here and there is going to be a major issue, as this happens in all walks of life.  It was the probability of all sounders failing at the same time.  Sounders failing I read this as the internal components on all the sounders within the building failing.  It's a probability and likely hood case.